- Abstract Polystyrene (PS)/cetyltrimethylammonium bromide (CTAB)/silica composites were prepared by CTAB-catalyzed in-situ polymerization of high internal phase emulsion gels (HIPE gels) at room temperature. The room temperature approach in HIPE gels yielded mono-dispersed PS/CTAB/silica spherical composite particles with sizes of 121 and 155 nm. The complex microscopic internal structures of these particles were determined with the use of temperature-modulated differential scanning calorimetry (TMDSC). CTAB, in particular, was identified in different environments within the composite particles based on its different crystallization temperatures observed on cooling: a thin layer at the surface of the fumed silica ( T C , CTAB = 74 °C), multilayers ( T C , CTAB = 82 °C), and a mixed PS/CTAB shell ( T C , CTAB = 65 °C). The amounts of each component were estimated from the enthalpies of the crystallization. The PS/CTAB mixed shell contained CTAB on the surface of the particle plus internal CTAB domains.